1. Field of the Invention
The invention relates to swimming pool cover systems and, in particular, to a drive utilizing a manually powered overrunning, one way clutch for alternatively rotating a cover drum and cable reel for retracting and extending a pool cover across a swimming pool.
2. Description of the Prior Art
Pool covers are used on many swimming pools. They save energy, keep the pool clean, minimize chemical use and provide desirable safety features. In fact, in windy locations, a pool cover is essential for maintaining pool water at comfortable temperatures at a reasonable expense.
The types of pool covering systems generally available commercially include free floating covers, tie down/stretched covers and track anchored floating covers. Mechanisms for retracting such covers back and forth across a pool include purely manual devices such as the "Rocky's" roller manufactured B. C. Leisure Ltd. 113-1305 Welch Street North Vancouver B.C. Canada V7P 1B3; semi-automatic systems (see U.S. Pat. No. 4,351,072) and automatic systems, which are usually electrically or hydraulically powered. (See U.S. Pat. Nos. 2,754,899; 2,958,083; 3,019,450; 3,050,743; 3,613,126; 3,982,286; 4,939,798 and 5,327,590).
Un-anchored floating pool covers typically serve as heat conservation blankets. Such floating blankets present a deceptive drowning hazard, particularly to young children and animals who often perceive the floating surface as being capable of providing support. Instead, the cover collapses, enfolds and entraps as the unlucky person, or animal sinks below the water surface. To alleviate such hazard, pools covered with un-anchored floating covers should be fenced and locked up when not in use, i.e., be treated as uncovered pool. Cover anchoring systems having separate fasteners for securing the perimeter of such floating covers to the pool deck are used in some cases to prevent a floating cover from enfolding and entrapping an inadvertent, unwary person or animal. However, such fastening systems tend to be very tedious and time consuming for properly securing a cover. Such lack of convenience lessens the likelihood of the cover being properly anchored. Improperly anchored floating covers present an even greater hazard as they reinforce an illusion of safety. Another disadvantage of floating and tie down pool cover systems is that when conditions are windy, they become extremely unruly to handle both on removal from and placement over the pool surface.
Recently, several manual pool cover systems have been marketed with typical extruded aluminum "C" channel swimming pool track for anchoring the side edges of the pool cover as is commonly done with automatic pool cover systems. The swimming pool track is secured on the pool deck along the sides of the swimming pool. The "C" channel of the track captures and holds a slidable beaded tape edge of the pool cover. The cover drum is manually rotated with a conventional crank (see the "Rocky" roller, supra) for retracting the cover from across the pool surface. However, as the cover winds onto the cover drum thereby increasing the diameter of the cover drum, the relative mechanical advantage of a crank handle turning the cover drum decreases. Accordingly, the effort required to turn the crank increases with increasing cover drum diameter. Similarly, the manual effort required to crank a cable reel for winding up a cable or line for extending a cover across a pool increases as the cover extends not only because of relative decrease in mechanical advantage of the crank, but also because of increasing friction resistance of the cover sliding in the track and across deck surface as it extends. Accordingly, such manual covers are typically extended across the pool by one preferably two or more persons pulling on ropes/cables extending from the front beaded tape edges of the cover. Such manual covers system are sometimes marketed as a temporary system which may later be stepped up to an automatic pool cover system by addition of a motor and/or cable reel system. In practice however, this rarely happens, and because of the physical effort involved, manual systems actually end up not being used once acquired.
Semi-automatic systems are only slightly more convenient than manual systems in that the cover drum is motorizing using electrical, hydraulic or spring motors for retracting the cover from across the pool. The pool covering fabric must still be pulled out manually by one or two operators and then secured by means of fasteners at the end of the pool, (and sides of the pool where track is not utilized to anchor the edges of the cover). In the case of a spring motor, in addition to overcoming the frictional load of the cover sliding in the track and across pool and deck surfaces, the operators must also wind the torsion spring of the spring motor.
Although effective and easy to use when properly maintained, some automatic pool cover systems are typically viewed and treated by consumers as troublesome contraptions prone to frequent failure. As performance degrades, frustrated pool owners sometimes overstress safety limits typically designed into such automatic motorized systems to preventing catastrophic failure. A stuck, halfway extended/retracted automatic pool cover not only causes grief for a pool owner but also for the repairman who must attempt to repair it while enduring the wrath of the pool owner. Automatic pool cover systems are also more expensive, and often beyond the means of homeowner families with toddlers.
Pool cover systems utilizing interconnected rigid buoyant slats which roll up on a submerged or elevated drum as described by U.S. Pat. No. 3,613,126, R. Granderath, popular in Europe, utilize passive forces arising from buoyancy or gravity for propelling, the cover extending it across a pool. In either instance, there must be some mechanism to prevent a retracted cover from unwinding responsive to the passive force. Such passive force systems also have a disadvantage in that the passive force must be overcome during retraction. Granderath suggests costly worm gear drive mechanisms for winding the cover and preventing cover drum rotation when not powered.
Another particular perplexing phenomenon in any coupled winding and unwinding system such as a pool cover--cable reel system, is that surface velocities of the respectively winding and unwinding elements vary as they wind and unwind from the respective rotating elements. (See Applicant's U.S. Pat. Nos. 5,184,357 & 5,327,590.) In the automatic pool cover systems of the type developed by Lamb, & McDonald (supra), bi-directional clutches of a type developed by W. W. Annable (U.S. Pat. No. 1,114,716) are used to alternatively couple a bi-directional drive motor to a cover drum when rotating one direction, and to a cable reel when rotating in the opposite direction. When not coupled to the motor by the bidirectional clutch, both the cover drum or cable reel respectively free wheel.
Creep is another phenomenon that must be addressed by any pool cover extension-retraction system. Creep results from the inherent resiliency or elasticity of the cover and cables. Such resiliency and rotational inertial of a spinning cable reel as the cover extends can cause cable backlash and snarling. In his co-pending application, Ser. No. 80/322,464 filed Oct. 14, 1994 entitled "ANTI-CAVITATION MANIFOLD FOR DRIVE COUPLED, DUAL MOTOR, REVERSIBLE HYDRAULIC DRIVE SYSTEMS" the Applicant describes a hydraulic manifold which hydraulically locks a driving hydraulic motor to inherently prevent creep from unwinding the winding element. See Applicant's U.S. Pat. Nos. 5,184,357 & 5,327,590 describing a dual hydraulic drive system where one reversible hydraulic motor is driven as a pump to provide a resistance load on the unwinding element for tensioning the cables and cover while the other reversible hydraulic motor rotates the winding element.! In cable length, spring compensation and tensioning systems pioneered by the Applicant under U.S. Pat. No. 3,982,286, Foster, (See Applicant's U.S. Pat. Nos. 4,939,590 & 5,067,184), the inherent resiliency and elasticity of the cables and cover are effectively compensated by the tensioning of the spring. In bidirectional clutch disengagement systems of the type developed by Lamb, a brake is utilized to resist and tension the unwinding cables as the cover is wound around the cover drum to preclude backlash and recoil and snarling of the cables due to the rotational inertial of the cable reel.
Regardless of the type of system used, pool size determining size and weight of a cover sheet of slat cover also imposes physical limits. This is particularly true of fastener secured covers where heavier vinyl and other fabrics are required. It is also true of floating thermal blankets. For, example, two or more persons are typically required to remove and place pool covers larger than 16'.times.32'. And, where a pool is wide or non-rectangular, pulling a cover over the water and deck surfaces is both awkward and hard. And, if the wind is blowing, manually removing placing or otherwise handling an unsecured cover can be quite dangerous.
The weight of water from rain or other external source collecting on the external surface of an extended cover sliding in and anchored along the sides of a pool by swimming pool track is also a problem. In particular, as the cover retracts, external water on the cover surface initially collects proximate and then is lifted up to pour over the top of the leading edge supporting the cover end above the pool surface. Unless removed before or as the cover retracts, weight of excessive external water on the cover surface can be sufficient to tear the beaded side edges of the cover from confining track channels, and catastrophically stall most cover winding mechanisms. Even with pour over systems as describe by Foster & Last, See U.S. Pat. Nos. 3,982,286; 4,939,798, & 5,067,184! additional torque is required of the drive system winding the cover to cause the water to pour out through the screen opening proximate the leading edge holding the cover end above the pool surface.
In instances where the cover drum and cable reel are anchored at a pool end for securing the cover, the cover drum should be close to or below the pool deck. In particular, the proximity of the cover drum surface to the track plane (the plane defined by the respective "C" channels of the swimming pool track fastened along the sides of the pool) determines the break-angle and hence frictional drag as the cover moves into out of the swimming pool track unwinding and winding around a cover drum. Also, the weight of a cover hanging from a wound up cover drum can cause it to unwind. See R. Granderath, supra! The space between surface of an exposed cover drum with the cover unwound and the pool deck also allows wind, dirt, debris, bugs, animals and toddlers to gain access under covered pool defeating many of the advantages and reasons for a cover in the first instance. Finally, aesthetics and design considerations demanded by pool owners require that all pool cover systems regardless of type, blend and not present trip hazards when the pool is uncovered and being used.
For manually rotated cover pool systems the degree of proximity of a cover drum to the pool deck surface limits the radius of conventional crank handles or wheels used to manually rotate the cover drum. Pool owners do not tolerate scraped knuckles well. And, as a practical matter, the cover drum must be enclosed both to prevent dirt and debris from blowing into a covered pool beneath the cover drum and to alleviate a trip hazard inherently presented by above deck pool cover anchored at one end of a swimming pool. Such cover drum enclosures limit access necessary for manually cranking or rotating a cover drum.
In contrast to above deck systems, locating a cover drum of a pool cover system in an covered trough or cover trench at one end of a pool, below the pool deck has the advantage of effectively isolating the pool, when covered, from blowing dirt and debris. Also locating a pool cover drum below the pool deck surface has an advantage of allowing the top rather than the bottom circumferential surface of the drum to be positioned relative to the track plane. And, if the swimming pool tracks for anchoring the sides of the pool cover are secured beneath the undercoping, the cover drum is most practically located below the pool deck.(See Applicants U.S. Pat. No. 5,439,707) However, placing manually cranked pool cover systems in a trough below a pool deck has not heretofore been considered feasible not only because of the inherent space limitations thereby further reducing the roller crank length and leverage, but also because most pool owners will not kneel down on a pool deck and then bend over to reach down to manually crank the cover drum in a trough below the pool deck even if it were possible.
Moreover, even with existing above deck, manually rotated, pool cover systems, pool owners are required to bend over or kneel to rotate a cover drum located just above the pool deck. Such bending or kneeling positions are not suitable postures for utilizing physical body strength. Nor are such postures recommended for the type strenuous work required of a pool owner to manually rotate a cover drum for winding up a pool cover. In particular, human beings most efficiently produce and transmit power via reciprocating linear arm and leg movements, typically using alternate left and right side body movements. Mechanisms for converting of such reciprocating linear human motion or effort into rotational motion are generally well known. See, for example, as U.S. Pat. No. 4,624,962, Street, entitled "Upper Body Exercise Mechanism", and U.S. No. Pat. 5,139,469, Hennessey entitled "Exercise Machine and Transmission Thereof."